Field of the Invention
The invention relates to an alignment ferrule which is made from injection molded plastic and is intended for use in a fiber optic connector or the like. Such ferrules are commonly referred to as 2.5 mm ferrules, and each such ferrule has a main axial passage to receive a fiber optic cable. The passage terminates in a very small diameter hole for receiving a projecting fiber optic member. In use, a pair of such ferrules are positioned in abutting relation in a fiber optic connector so a corresponding pair of fiber optics may be precisely abutted in end-to-end relation for transmission of an optical signal.
The effectiveness of such a connection between two or more fiber optic members depends upon the precision of the alignment of the abutting fiber optic members. If such fiber optic members are not precisely aligned with one another, a resulting loss of signal will impair the effectiveness of the connection. Due to the minute tolerances associated with fiber optic connectors, known molding technology has not been able to produce products within specified limitations. Known molding technology yields tolerances to the fourth decimal point at best, whereas fiber optic technology demands tolerance limitations to at least the fifth decimal point. Therefore, one object of the present invention relates to a method and apparatus for adjusting out excessive tolerances associated with known molding technology.
The present invention relates to a combination of adjustable core and receiver members which serve to precisely locate a core pin and also a projecting wire member in a mold for purposes of injection molding of alignment ferrules of the type above described. As is known in the art, such a core pin is positioned in the mold, and plastic material is molded around the core pin during a molding operation to form the desired 2.5 mm plastic ferrule. Thus, a portion of the body of the core pin defines an axial opening or passage in the ferrule for receiving a fiber optic cable. In addition, the small diameter wire projecting from one end of the core pin defines a small diameter hole at one end of the molded ferrule which receives and holds the fiber optic member which is to be precisely aligned with a like fiber optic member in a fiber optic connector or the like.
A method intended to increase the accuracy of molding a conical connector plug for a biconical fiber optic connector is shown in U.S. Pat. No. 5,034,170. The method disclosed in the '170 patent is for molding of a hollowed-out, apertured, conical plug which has a projecting pedestal at its small or forward end and a small diameter longitudinal hole in the pedestal to hold and position a projecting fiber optic member. The foregoing patent in FIG. 2 shows use of a pair of inner and outer conical cams 40 and 42 to increase the accuracy of the pedestal hole relative to the axis of the molded plug.
More specifically, the '170 patent in FIG. 2 shows a core pin 36 having a forward conical end in which is mounted a stepped pin 38. The stepped pin 38 comprises an extension of the core pin 36 and its smallest end projects into a small hole formed at the base of a recess 39 formed in the front face 43 of an inner cam member 40. By selective rotation of the inner and outer cams 40 and 42, the small hole at the base of the indentation 39 in the front face 43 of the inner cam 40 can be moved to a desired location relative to the longitudinal axis of the mold cavity which forms the plug 32.
By repositioning that hole into which the small end of the stepped pin 38 projects, it is possible to control the position of the small end of that stepped pin and thereby control with increased accuracy the location of the hole which is formed in the molded pedestal on the front of the molded plug 32. In the foregoing manner, it is possible to control the location of the axis of the pedestal hole relative to the axis of the plug profile.
The present invention is significantly different from the disclosure in U.S. Pat. No. 5,034,170 in many significant respects. According to the present invention, a pair of inner and outer rotatable nested cylinders are used to increase the accuracy of locating a hole in the mold fixture. However, beyond that there is little similarity in the respective inventions.
According to the present invention, the object to be molded is an alignment ferrule which is generally cylindrical in configuration and has a relatively large passage to receive a fiber optic cable, the passage being in communication with a small longitudinal hole to receive and position a fiber optic which is to be abutted with another such fiber optic in a connector or the like.
The present invention relates to a method and apparatus for injection molding of a plastic alignment ferrule. The apparatus includes two different nested cylinder assemblies, and each assembly preferably comprises a pair of inner and outer cylinders which are both rotatable and where the inner cylinder includes an eccentric locating aperture in its end face for receiving and positioning a mold element. Rotation of the outer cylinder will carry the inner cylinder with it thereby causing the eccentric aperture in the end face of the inner cylinder to move to its true center on the "Y" axis. Rotation of the outer cylinder while holding the inner cylinder will cause the eccentric aperture in the end face of the inner cylinder to move to its true center on the "X-Y" axis. Accordingly, by a combination of cylinder rotations, the locating aperture in the end face of the inner cylinder may be located precisely in a desired position.
An important feature of the present invention involves the use of two nested cylinder assemblies of the foregoing type. A first assembly includes an inner cylinder having a relatively large opening to receive and support a core pin which is used as a mold element to form an internal fiber optic cable passage in a molded plastic ferrule. A second assembly includes an inner cylinder having a very small hole to receive and support a small wire which projects axially from the end of the core pin, whereby operation of the second assembly will serve to locate the projecting wire in a precise manner.
Thus, in accordance with the present invention there are two nested cylinder assemblies which respectively locate independently and in a precise manner both a core pin and also a small wire projecting from one end of the core pin. In the foregoing manner, it is possible to assure that not only the core pin itself is accurately located and aligned relative to the mold cavity for molding the plastic ferrule, but also there is an independent cylinder assembly which controls in a precise manner the location of a small wire which projects from the end of the core pin and serves the purpose of defining a tiny hole in the molded ferrule for receiving and locating a fiber optic which projects from a fiber optic cable and is to be abutted in precise mating relation with a like fiber optic in a fiber optic connector.
In accordance with the invention as above described, one inner cylinder member adjusts the position of a core pin in a mold, and a second inner cylinder member adjusts the position of a projecting wire which projects from the forward end of the core pin. The mold parting line is transverse to the longitudinal axis of the mold cavity with the result that the foregoing projecting wire will repeatedly be inserted and withdrawn from the small eccentric hole in the second inner cylinder member as the mold is closed and opened. However, it is preferred to have the mold halves open and close in the direction of the longitudinal axis of the molded alignment ferrule to avoid any parting line flash on the outer diameter of the molded ferrule. The adjustable core and receiver concept of the present invention thus involves adjustment of both the core and the receiver to their true centers by mounting both the core pin and receiver into corresponding inner eccentric cylinders.
In accordance with a feature of the present invention, the adjustment of the core pin and the receiver are accomplished when the mold is removed from a molding press and each of the two cylinder assemblies is located in a respective half of the mold. Such adjustment is accomplished by use of known inspection equipment whereby an operator can locate the eccentric hole in each of the two inner cylinders into a desired position and then lock the two inner cylinders in position to precisely locate independently both the core pin itself and the projecting wire member when the mold halves are subsequently inserted into a molding press and closed. The foregoing contrasts with the method disclosed in U.S. Pat. No. 5,034,170 where the adjustment is made while the mold is positioned in a molding press. The method and apparatus of the present invention have application to 2.5 mm single mode and multimode fiber optic technology.
The primary object of the present invention is to provide a combination of adjustable core and adjustable receiver means for use in the molding of alignment ferrules known as 2.5 mm ferrules so as to assure not only the precise location in the mold of a core pin per se, but also to independently assure the precise location of a small diameter wire projecting from the core pin. In the foregoing manner, not only is the projecting wire precisely located, but in addition the wire is maintained in a straight or longitudinal position due to the independent longitudinal alignment and positioning of the core pin from which the wire projects.
The foregoing and other objects and advantages of our invention will be apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings.